Evaluating spatial and temporal variability in soil erosion risk -: rainfall erosivity and soil loss ratios in Andalusia, Spain

Erosion modeling techniques provide a framework for the evaluation of agricultural impacts on soil and water resources. Agricultural policies or economic incentives generally induce land use changes or even agricultural crop rotation changes. This results in a different erosional behavior of cultivated soil. Besides economic benefits, the sustainability of the agricultural practices with regard to soil and water resources has to be evaluated for specific local or regional conditions. This paper analyzes the spatial and temporal variability in soil erosion risks in a changing Mediterranean agro-ecological situation. At first the spatio-temporal variability of rainfall erosivity is analyzed. The depth and erosivity of design storms are determined for different return periods. Then, the temporal variability of soil loss ratios (SLR) due to different agricultural crop rotations are evaluated on watershed scale using the revised universal soil loss equation (RUSLE). The 211 km(2) Guadalteba river basin and study area is located in the region of Andalusia, southern Spain, presenting a typical south European agricultural wheat and oil producing area with marked occurrence of soil erosion problems. The spatial soil erosion risk evaluation approach is based on commonly available data and a minimum of additional field observations. The spatial distribution of input and output data is handled with the Integrated Land and Water Information System (ILWIS). (C) 1999 Elsevier Science B.V. All rights reserved.